
.... is thicker than water.
A child who doesn't have any brothers or sisters
families where the mother or father is bringing up the childred on his/her own
your uncle's or aunt's children
Your grandparents' parents are your great-great-grandparents
the new wife of your father is ...
boys who have the same father but a different mother
a child is legally taken by another family to be taken care of as their own child